The Field Strength Metrology Project develops measurements of free-space electromagnetic (EM) emissions to help evaluate electronic interference of electronic devices and systems. The project maintains the link to the International System (SI) of Units for EM field strength measurements. The project also provides information to standards organizations to help correlate measurements between various electromagnetic compatibility (EMC) test facilities. Our goal is to develop and evaluate reliable and cost-effective standards, test methods, and measurement services related to complex EM fields for EMC electronic devices and other health, defense, and homeland security applications.
NIST calibrates electrically-small field probes from 10 megahertz – 40 gigahertz. These measurements are done in facilities that are periodically compared against other National Metrology Institutes in conjunction with the Bureau International des Poids et Mesures (BIPM). This assures international agreement in their performance and reduces uncertainties in these important areas of metrology that affect international trade.
EM field strength measurements are done in several types of chambers: transverse electromagnetic TEM cells, gigahertz TEM (GTEM) cells, and a fully anechoic chamber. The project is working on test methods for modulated field strength and time-domain measurements. The project is also developing field strength test methods for probes that can operate at frequencies above 40 gigahertz, as the industry moves towards employing higher frequencies in a wide range of applications. The Field Strength Metrology Project is also developing a Rydberg atom-based field probe for independent, absolute field strength measurements. This atom-based probe could greatly improve the accuracy and reduce the uncertainties in field strength probe calibrations.